Hydraulic system of lathes and other metal working machines, presses, and the like



Nov. 13, 1956 J. ANDERSON HYDRAULIC SYSTEM OF LATHES AND OTHER METAL WORKING MACHINES, PRESSEIS, AND THE LIKE Filed April 30, 1954 United States Patent HYDRAULIC SYSTEM OF LATHES AND OTHER METAL WORKING MACHRNES, PRESSES, AND THE LIKE James Anderson, Newton Mearns, Scotland Application April 30, 1954, Serial No. 426,795

Claims priority, application Great Britain May 13, 1953 2 Claims. (Cl. 121-38) This invention has reference to the hydraulic system of lathes and other metal-working machines, presses and the like.

In lathes and other metal-working machines provided with an hydraulic feed the hydraulic feed embodies a piston and cylinder assembly and a control valve by the operation of which fluid under pressure can be admitted to act on the head of the piston so that the latter is moved forward under pressure to eflect the feed stroke, the further operation of the control valve placing the cylinder open to exhaust so that the piston is returned to its initial position by the pressure fluid which continuously tends to return the piston to such position.

Hydraulic presses are provided with a substantially similar hydraulic system.

In such machines and presses it is necessary that the operator should operate the control not only to eflect the power stroke but also to effect the return stroke.

The present invention has for its object to provide improvements relating to the hydraulic feed of a lathe or other metal working machine, hydraulic press or the like whereby, when the pressure on the piston head rises to a predetermined extent, the supply of pressure fluid to the piston head will be cut off automatically and thereafter the fluid acting on the piston head exhausted.

Preferably the pressure is transmitted to the piston through a flexible diaphragm to decrease friction of the snap action valve.

An embodiment of the invention will now be described with reference to the annexed drawings wherein Figure 1 shows diagrammatically the hydraulic feed system of a lathe or metal-working machine in accordance with the invention and Figure 2 shows to a larger scale the control valve thereof.

The hydraulic system illustrated embodies a cylinder with diflerential piston 11 working therein, said cylinder being connected to a fluid pressure supply line 12 through a control valve 13.

The pressure supply is also connected through a pipe line 14 with the annular chamber 15 formed below the piston head so that the pressure fluid acting on the annular underface of the piston always tends to return the piston to its initial position.

The control valve 13 is provided with a cylindrical valve body 16 having three ports 17, 18, 19, port 17 being connected to the pressure supply line 12, port 18 connected by a pipe line 20 leading to the top of said cylinder 10 so that the fluid supplied thereto will act on the head of the piston therein and the port 19 connected to an exhaust pipe line 21 leading to the sump.

Within said valve body is a balanced shuttle piston valve in the form of a cylinder 22 recessed to form a central annular chamber 23 and also two end annular chambers 23 and 24. One end of this balanced valve is provided with a knob or the like 25 by which it can be moved axially manually, a small spring-loaded plunger 26 being arranged to engage with either of two annular recesses 27 and 28 in the valve to retain it in either of its two positions. Said valve is provided with a central bore 29, closed at one end and open at the other end which is adjacent to an end cover plate 30 having a spring-loaded non-return ball valve 31 controlling a passage therein connected by pipe line 32 to a snap action valve 33.

The said bore communicates by means of radial passages 34 and 35 with the two end annular chambers 23 and 24.

The snap action valve 33 comprises a valve body 36 containing a spring-loaded piston valve 37 and a base 38, a flexible diaphragm 39 being clamped between the valve body and its base so as to bear on the piston. A nut 40 screwed within the valve body bears on and regulates the compression in a compression spring 41 encircling the valve spindle.

The said base is provided with a bore 42 of a diameter small with respect to that of the piston and which bore is in communication with the pipe line 20 leading to the cylinder 10. The base is formed with a shallow annular recess 43 surrounding the valve seat 44 which latter is normally sealed by the diaphragm. The base is also provided with a port communicating with said recess and to which is connected the pipe line 32.

The said annular recess in the base is provided with a small outlet port which can bleed through pipe line 45 into the pipe line 21 leading to the sump.

The spring on the snap action valve is first adjusted so that this valve will not open at the pressure normally existing in cylinder 10 during the power stroke.

To move the tool-carrying slide to eflect the cutting operation the balanced piston valve is moved axially so that the pressure fluid supplied to its central annular recess 32 passes through pipe line 20 to the cylinder 10 and drives outwardly the piston 11 therein, the piston being moved against the pressure of the fluid on the annular rim on the other side of the piston.

When the piston is arrested at the end of its stroke pressure will build up in the cylinder 10, such pressure being transmitted to act on the small area of the diaphragm which normally seals the bore 42 and when said pressure overcomes the spring-loading, the diaphragm is moved to uncover the said bore and the accumulated pressure is then applied to the full area of the diaphragm. Immediately this occurs the diaphragm and springloaded piston valve 37 are moved to the fully open position. A short quick flow or surge ofpressure fluid ocours in the pipe line 32 connecting the snap action valve with the end of the control valve, the fluid passing through the non-return valve 31 to impart an impulse to the end of the balanced piston control valve. As the control valve is balanced, the two annular chambers being in communication with each other, this impulse moves the control valve sharply to its initial or off position whereon the supply of pressure fluid to act on the piston head is stopped and the cylinder above the piston head placed in communication with the pipe line 21 leading to the sump. The pressure fluid acting on the annular rim on the underside of the piston returns the latter to its initial position.

Should the tool-carrying slide meet with abnormal resistance, as would occur for example when the cutting edge of the tool is broken, a pressure will be built up in the cylinder and such pressure will operate the snap action valve which will then function to move the control valve to the off position as above described. That is, the snap action valve will perform the function of an overload or safety device to stop the feed movement in certain eventualities.

The piston rod of the snap action valve may operate a switch 46 in the motor circuit of the machine so that when said valve is operated by accumulated pressure, it will simultaneously cut out the motor.

In the event of the pressure fluid bleeding into the annular recess of the snap action valve no pressuresufficient to operate this valve can accumulate therein as such fluid passes to the pipe line 45 leading tothe sump.

I claim:

1. In a lathe, metal working machine, hydraulic presses and the like an hydraulic feed system comprising a cylinder with difierential piston working therein, a control valve comprising a valve body and a manually operable shuttle valve member working therein, means whereby, irrespective of the position of the shuttle valve member, hydraulic pressure fluid supplied to the valve body is fed to said cylinder to act on the annular face of the differential piston, means by which, on the manual operation of the shuttle valve member in one direction pressure fluid is also fed to act on the head of the differential piston to effect the feed of the lathe, press and the like, means by which, when the shuttle valve member is moved in the other direction the supply of pressure fluid to act on the piston head is interrupted and thereafter the fluid acting on the piston head is opened to exhaust and means to move the shuttle valve member in such other direction comprising a snap action valve sensitive to the pressure of the fluid acting on the piston head and controlling the passage of pressure fluid to act on the end of the v mits the fluid acting on the piston head to exhaust.

2. A machine, press or the like having an hydraulic system as claimed in claim 1 wherein the snap action valve is provided with a spring-loaded piston which forms the valve proper and which seats on a valve seat of substantially smaller diameter, the construction being such that when the piston is raised oil its seat against the act-ion of its spring and under the action of the accumulated pressure of the fluid transmitted thereto said fluid immediately acts on the full area of the piston so that the latter moves with a snap action to its fully open position.

References Cited in the file of this patent UNITED STATES PATENTS 840,877 Steedman Jan. 8, 1907 1,660,720 Osborne Feb. 28, 1928 1,808,431 Osborne June 2, 1931 

